When a directional antenna is installed, it is important that the antenna faces toward an appropriate direction in which the reception level becomes the maximum. When an operator installs the antenna, the operator changes the direction in which the antenna faces so that it faces various directions to find the direction in which the reception level becomes the maximum so as to be able to install the antenna so that the antenna faces toward this direction. As a matter of course, even after the antenna is installed, the antenna needs to constantly face toward the direction in which radio waves are coming.
For example, Patent literature 1 (Japanese Unexamined Patent Application Publication No. 6-1023345) discloses a receiving device that automatically tracks satellite broadcast waves. This receiving device is installed, for example, in a vehicle such as an automobile. The receiving device includes an antenna, a swing mechanism which pivotally drives the antenna, and a gyro sensor that detects a variation amount of a traveling direction of the vehicle. When the gyro sensor detects that there has been a change in the traveling direction of the vehicle, the swing mechanism swings the antenna in a direction opposite to the direction in which there has been a change in the traveling direction of the vehicle. According to this configuration, even when there is a change in the traveling direction of the vehicle, the antenna constantly faces toward the direction of the satellite.